Revert the timeline optimistic and pagination rework (#2596)

* Add npm release track invariant and beta dist-tag procedure

* Revert "Keep older chat history and image previews stable (#2490)"

The timeline optimistic/pagination rework needs more work than main releases can wait for. Reverted together with #2484; both are reapplied on integration/timeline-optimistic-rework.

* Revert "Stop completed turns from appearing stuck (#2484)"

See the #2490 revert. #2490 built on this submission-authority change, so the two revert and reapply as a pair.

packages/app/src/assistant-image/retry.test.ts

@@ -1,49 +0,0 @@
-import { describe, expect, it } from "vitest";
-import { runAssistantImageOperationWithRetry } from "./retry";
-
-describe("assistant image retry", () => {
-  it("recovers from transient failures while the image remains mounted", async () => {
-    const waits: number[] = [];
-    let attempts = 0;
-
-    const result = await runAssistantImageOperationWithRetry({
-      operation: async () => {
-        attempts += 1;
-        if (attempts < 3) {
-          throw new Error("transient");
-        }
-        return "loaded";
-      },
-      delaysMs: [10, 20, 30],
-      wait: async (delayMs) => {
-        waits.push(delayMs);
-      },
-    });
-
-    expect({ attempts, waits, result }).toEqual({
-      attempts: 3,
-      waits: [10, 20],
-      result: "loaded",
-    });
-  });
-
-  it("stops retrying after the image is released", async () => {
-    let stopped = false;
-    let attempts = 0;
-
-    await expect(
-      runAssistantImageOperationWithRetry({
-        operation: async () => {
-          attempts += 1;
-          throw new Error("transient");
-        },
-        delaysMs: [10, 20],
-        shouldStop: () => stopped,
-        wait: async () => {
-          stopped = true;
-        },
-      }),
-    ).rejects.toThrow("transient");
-    expect(attempts).toBe(1);
-  });
-});